[18F]PI-2620 Phase 3 Histopathological Study

Inclusion Criteria:

Only subjects who meet all of the following criteria will be eligible for enrollment into the study:

1. Males and females aged 50 years and over

2. Have a projected life expectancy of ≤ 1 year as determined by the investigator (terminal medical condition including but not limited to end-stage dementia,end-stage congestive heart failure, end-stage chronic obstructive pulmonary disease (COPD), or end-stage cancer)

3. Written informed consent obtained from the subject and/or the subject's legallyauthorized representative (LAR), as applicable, to consent for study procedures andbrain donation (consent consistent with the legal requirements of the State in whichthe subject dies)

4. Can tolerate study procedures including lying down in PET scanner. The investigatorwill carefully assess each subject and use medical judgment to determine whether thesubject can tolerate the imaging procedure

Exclusion Criteria:

Subjects will be excluded from the enrollment if they:

1. Are receiving aggressive treatment with life sustaining measures (e.g. receivingchemotherapy; palliative chemotherapy is allowed)

2. Are known to have a structural brain lesion that would interfere either with PETimaging or pathological assessment (e.g. lesions are typically > 2 cm at theirgreatest extent and may include stroke, primary or metastatic neoplasm, other tumorsor cystic lesions. Subjects with a history of major stroke or traumatic brain injuryor other structural lesion as well as cases with a history of primary CentralNervous System (CNS) neoplasm or known metastatic cancer must be discussed with thestudy sponsor prior to enrollment)

3. Have suspected encephalopathy due to alcoholism or end-stage liver disease

4. Are known to have a Glomerular Filtration Rate below < 15 mL/min

5. Have received an investigational or approved therapy directly targeting amyloid ortau

6. Are females of childbearing potential who are pregnant, lactating or breastfeeding,or who are not using adequate contraception

7. Have implants such as implanted cardiac pacemakers or defibrillators, insulin pumps,cochlear implants, metallic ocular foreign body, implanted neural stimulators, CNSaneurysm clips and other medical implants that have not been certified for MRI, orhistory of claustrophobia in MRI (in case an MRI is planned to be performed)